Effect of Variable Frequency Drive and Pipe Materials on Guava Juice Flow

In this study, a designed variable frequency drive (VFD) was used to control a single-phase induction motor’s speed to pump guava juice at two solid concentrations (9°Bx and 11°Bx). Next, the pressure drop was measured in stainless-steel pipes of three diameters. The pressure drop percentage difference before and after using the VFD at varied flow rates with 10 repetitions at 5-minute intervals was evaluated. The pressure drop reduction range was 19.7%– 30.8% and 19.2 %–32.4% for the 9% and 11% solid concentrations respectively after using the VFD, which resulted in an average of 25.73% reductions in pressure drop and the pump’s total head and driving power. The rheological properties of guava juice were investigated at various temperatures (5, 15, 25, 35, 55 and 75°C). From the results, all materials exhibited non-Newtonian pseudoplastic behavior at all temperatures and concentrations, and correlated well with the power law model, with flow behavior index (n) values less than unity for the 9% and 11% solid concentrations. The findings offer helpful information for predicting how heat variations during processing influence the behavior of guava juice concentrates.